Introduces a `uiTextEditing` struct to hold most data for handling text editing,
with improved naming. This should help untangling this code a bit, reduce
perceived complexity, and make the relation between data and the button state
more clear.
Generally I'd like to try to minimize use of `uiHandleButtonData`, to reduce
complexity while increasing flexibility. For example it would be good if text
editing code could be independent of the active button, so a text button can
receive input while other UI elements remain interactive (e.g. for search
popups, which have their own ad-hoc layout, event handling and drawing code).
This is a rather conservative initial refactor, I might follow up with further
(more risky) changes in separate PRs. But this seems like enough of an
improvement to get in first.
Pull Request: https://projects.blender.org/blender/blender/pulls/122332
44e9544199